A number of applications exist for equipment that is capable of delivering predetermined quantities of fluid, as in the form of a liquid or semiliquid, which consists of a precise, fresh mixture of several components. Considering applications, a variety of resins and other synthetic materials, as silicon rubber, are formulated from a plurality of components. For example, a variety of synthetic materials involve a precise combination of two distinct components which, once combined, will react and solidify to a desired physical form. As a specific example, polymers are widely used in combination with catalysts which together cure, achieving vulcanization and providing a rubber-like solid substance. For some materials, the ratio of the individual components is highly critical; however, for almost all of such materials, precise volume measurements in the mixture are desirable in attaining the product.
Over the years a vast number of meter-mix structures have been proposed for handling fluids in the form of liquid or semiliquid materials. However, a need is deemed to continue to exist for an effective meter-mix machine to deliver a multicomponent material and that is capable of delivering metered quantities of material consisting of a precise, fresh mixture. In various applications, metered quantities of material can serve to fill mold cavities or otherwise be provided to a variety of forming apparatus.
One class of meter-mix equipment as employed in the past has utilized check valves to control the flow of liquid components which subsequently are combined in the mixture. Specifically, for example, two liquid components may be drawn through check valves (which are connected to sources of the fluid) so as to load pumps that are discharged through another pair of check valves into a mixing chamber. Although these arrangements are effective for a variety of mixtures; certain difficulties arise in using such apparatus where precise mixtures are desired. Specifically, one of the problems of such apparatus arises because the check valves may not operate in complete synchronism. That is, pressure or mechanical differences may cause the check valves associated with the control of one liquid component to operate at instants of time that are somewhat offset from the operating times of the check valves controlling the other liquid. As a consequence, the component ratio tends to vary with each discharge and furthermore, the volume of each discharge varies. Consequently, a need exists for an effective, economical, durable and reliable meter-mix machine that will deliver precise discharges of fresh mixtures in consistent volumes.
In general, the present invention comprises a meter-mix machine utilizing positively acting valves which are synchronously operated to accomplish precise control. The positive valves are actuated by individual gear wheels that are rotated by a common drive. The control system of the machine senses the position of the valves as well as the position of a metering apparatus which includes a pump-like metering structure for each fluid component. The sensed data, in the form of control signals, is employed to control the valves and the stroke reversals of the metering structures.